Hassas Nokta Konumlama Tekniğinin Hidrografik Ölçmelerde Kullanılabilirliği

Bu çalışmada, hassas nokta konumlama Precise Point PositioningPPP yönteminin dinamik ortamlardaki performansını test etmek üzere bir dizi çalışma gerçekleştirilmiştir. Bu kapsamda İstanbul Haliç’te bir tekneyle yaklaşık 2 saat süren bir uygulama yapılmıştır. Tekneye konulan jeodezik çift frekanslı GPS antenine bir anten splitter yardımıyla çift frekanslı jeodezik Ashtech Z-Xtreme ve tek frekanslı OEM tipi tek frekanslı GPS alıcısı Ashtech AC12 bağlanmıştır. Antenin rölatif yöntemle koordinatını belirlemek için kıyıda tesis edilen koordinatı bilinen bir noktaya da bir başka jeodezik GPS alıcısı kurulmuş ve veri toplanmıştır. Kıyıdaki ve teknedeki jeodezik GPS alıcıları ile toplanan verilerden yararlanarak antenin konumu cm mertebesindeki doğrulukla belirlenmiştir. Teknede hem jeodezik hem de OEM alıcıları ile toplanan veriler Kanada CSRSPPP servisine gönderilerek her bir ölçme anının epoch PPP yöntemi ile koordinatı belirlenmiş ve bu koordinatlar rölatif yöntemden elde edilenlerle karşılaştırılmıştır. Değerlendirme sonucunda, tek frekanslı düşük maliyetli OEM tipi alıcıdan elde edilen sonuçların, rölatif yönteme 1-2 metre doğrulukla yakınsadığı görülmüştür. Çalışmada kullanılan çift frekanslı alıcı ile toplanan veriler değerlendirilirken yazılım, hem faz hem de kod ölçülerini kullanmakta olduğundan daha yüksek mertebede doğruluklara 1-2 dm ulaşılmıştır. Elde edilen bu sonuçlar söz konusu yöntemin birçok hidrografik ölçme uygulamasında gereksinim duyulan doğrulukları karşılayabilecek düzeyde olduğunu göstermiştir.

Usability of Precise Point Positioning PPP Technique In Hydrographic Surveying

In this study, a series of studies were conducted in order to test the performance of the Precise Point Positioning PPP Technique in marine applications dynamic environments . 2-hour measurements were carried out in Haliç, İstanbul in this context. A dual frequency geodetic GPS antenna, located on the vessel, was connected to a dual frequency geodetic grade GPS receiver Ashtech Z-Xtreme and an OEM single frequency GPS receiver Ashtech AC12 via an antenna splitter. Another geodetic GPS receiver was set up on a reference point on the shore for relative positioning of the antenna. The coordinates of the antenna were calculated in cm accuracy level using the data gathered by the geodetic GPS receivers on the vessel and at the shore. Coordinates of each epoch were calculated with the PPP technique by sending the data to the on-line GPS processing service, CSRS-PPP, gathered by both the geodetic and OEM receivers and the PPP-derived coordinates obtained from the service were compared with the ones calculated by relative positioning. According to the assessments, results obtained from single frequency low-cost OEM receivers converges the results of the relative positioning results within 1-2 meters of positioning accuracy. The results from dual frequency receivers meet at decimeter-level positioning accuracy level the service used code and carrier phase data when dual frequency data is available. The obtained results show that the proposed method is able to meet the accuracy requirements in several hydrographic surveying applications.

___

  • ABIDIN, H.Z. ve MUCHLAS, A.: GPS Surveying Using Navi- gation Type Receivers, Proc. of the South East Asia Survey Congress 2005, Bandar Seri Begawan, Brunei Darussalam, 21- 25 November 2005.
  • ALKAN, R.M., EL-RABBANY, A. ve SAKA, M.H.: Assessment of Low-Cost Garmin OEM GPS Receiver for Surveying Applications, Ontario Professional Surveyor, 49(4), 2006, 14- 16, Canada.
  • ALKAN, R.M., EL-RABBANY, A. ve SAKA, M.H.: Low Cost Single–Frequency GPS for Surveying: A Performance Analysis, Location, 2(2), 2007, 28-31, India.
  • ALKAN, R.M., SAKA, M.H., KALKAN, Y. ve ŞAHIN, M.: Usabil- ity of Low-Cost L1 Frequency GPS Receivers in Surveying Applications, European Navigation Conference (ENC-GNSS), Proc. of the Toulouse Space Show’08, Toulouse, France, 22-25 April 2008.
  • ALKAN, R.M. ve SAKA, M.H.: A Performance Analysis of Low- Cost GPS Receivers in Kinematic Applications, Journal of Navigation, 62 (4), 2009, 687–697, UK.
  • CHOY S.L., ZHANG K., SILCOCK D. ve WU F.: Precise Point Positioning - A Case Study in Australia, Proc. of Spatial Sci- ences Institute International Conference (SSC2007), pp. 192- 202, Hobart, Tasmania, Australia, 2007.
  • COSSER, E., HILL, C.J., ROBERTS, G.W., MENG, x., MOORE, T. ve DODSON, A.H.: Bridge Monitoring with Garmin Hand- held Receivers,Proc. of the 1st FIG International Symposium on Engineering Surveys for Construction Works and Structural Engineering, Nottingham, United Kingdom, 2004.
  • EL-RABBANY, A.: Introduction to GPS, The Global Positio- ning System, Artech House, Second Edition, ISBN-13: 978- 1596930162, 2006.
  • GAO, Y. ve SHEN, x.: A New Method for Carrier-Phase–Based Precise Point Positioning, Navigation, 49(2), 2002, 109-116, USA.
  • HILL, C.J., MOORE, T. ve DUMVILLE, M.: Carrier Phase Sur- veying with Garmin Handheld GPS Receivers, Survey Revi- ew, 36(280), 2001, 135-141, UK.
  • KOUBA, J.: A Guide to Using International GPS Service (IGS) Products, IGS Central Bureau, (on-line publication at URL: http://igscb.jpl.nasa.gov/igscb/resource/pubs/GuidetoUsin- gIGSProducts.pdf), 2003.
  • KOUBA, J. ve HÉROUx, P.: Precise Point Positioning Using IGS Orbit and Clock Products, GPS Solutions, 5(2), 2001, pp. 12-28, Germany.
  • MASELLA, E.: Achieving 20 cm Positioning Accuracy in Real Time Using GPS-the Global Positioning System, GEC Revi- ew, 14(1), 1999, 20-27.
  • MASELLA, E., GONTHIER, M. ve DUMAINE, M.: The RT- Star: Features and Performance of a Low-Cost RTK OEM Sensor, The International Technical Meeting of the Satellite Division of the ION, Proc. of the ION GPS’97, pp. 53-59, Kan- sas City, Missouri, 16-19 September 1997.
  • RIZOS C., HAN S. ve HAN x.: Performance Analysis of a Single-Frequency, Low-Cost GPS Surveying System, GPS ION’98, Proc. of the 11th Int. Tech. Meeting of the Satellite Division of the US ION, pp.427-435, Nashville, Tennessee, 15- 18 September 1998.
  • SAEKI, M. ve HORI, M.: Development of an Accurate Positio- ning System Using Low-Cost L1 GPS Receivers, Computer- Aided Civil and Infrastructure Engineering, 21(4), 2006, 258- 267.
  • SCHWIEGER, V. ve GLÄSER, A.: Possibilities of Low Cost GPS Technology for Precise Geodetic Applications, Proc. of the FIG Working Week 2005, Cairo, Egypt, 16-21 April 2005.
  • SÖDERHOLM, S.: GPS L1 Carrier Phase Double Difference Solution Using Low Cost Receivers, ION GNSS 2005, Proc. of the ION GNSS 18th International Technical Meeting of the Satellite Division, pp.376-380, Long Beach, CA, 13-16 Sep- tember 2005.
  • WESTON, N.D. ve SCHWIEGER, V.: Cost Effective GNSS Po- sitioning Techniques, FIG Commission 5 Publication, ISBN 978-87-90907-79-2, Denmark, 2010.
  • ZUMBERGE, J.F., HEFLIN, M. B., JEFFERSON, D. C., WAT- KINS, M. M. ve WEBB, F. H.: Precise Point Positioning for the Efficient and Robust Analysis of GPS Data from Large Networks, Journal of Geophysical Research, 102(B3), 1997, pp. 5005-5017, USA.